U.S. patent application number 11/255938 was filed with the patent office on 2006-05-04 for method of detecting high-concentration region direction of pollutant in soil.
This patent application is currently assigned to Canon Kabushiki Kaisha. Invention is credited to Yasuhisa Fujii, Naoya Ichimura, Shigekazu Shimizu, Yasuo Takahashi, Tokugen Yasuda.
Application Number | 20060090539 11/255938 |
Document ID | / |
Family ID | 36260268 |
Filed Date | 2006-05-04 |
United States Patent
Application |
20060090539 |
Kind Code |
A1 |
Takahashi; Yasuo ; et
al. |
May 4, 2006 |
Method of detecting high-concentration region direction of
pollutant in soil
Abstract
A recovery phenomenon in which the concentration of a compound
to be measured in soil increases again after reducing the
concentration is utilized for changing the distribution state of
the compound to be measured in soil, whereby the direction of the
high-concentration region of the compound to be measured in soil
can be detected.
Inventors: |
Takahashi; Yasuo; (Tokyo,
JP) ; Shimizu; Shigekazu; (Kitaadachi-gun, JP)
; Ichimura; Naoya; (Uji-shi, JP) ; Fujii;
Yasuhisa; (Kyoto-shi, JP) ; Yasuda; Tokugen;
(Kyoto-shi, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
Canon Kabushiki Kaisha
Tokyo
JP
|
Family ID: |
36260268 |
Appl. No.: |
11/255938 |
Filed: |
October 24, 2005 |
Current U.S.
Class: |
73/19.09 |
Current CPC
Class: |
G01N 33/24 20130101 |
Class at
Publication: |
073/019.09 |
International
Class: |
G01N 33/24 20060101
G01N033/24 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2004 |
JP |
2004-315845 |
Jul 22, 2005 |
JP |
2005-212918 |
Claims
1. A method of detecting a direction of a high-concentration region
of a compound to be measured in soil, comprising utilizing a
difference in diffusion change of a concentration of the compound
to be measured in soil from a high-concentration region and a
low-concentration region in a recovery phenomenon in which a
concentration of the compound increases again after reducing the
concentration.
2. The method according to claim 1, wherein the compound to be
measured is a chlorinated organic compound such as
trichloroethylene or tetrachloroethylene.
3. The method according to claim 1, wherein the detection is
carried out using a frequency-converting element.
4. The method according to claim 3, wherein the
frequency-converting element comprises one electrode having a
surface coated with a material for adsorbing the compound and the
other electrode having a surface coated with an electrically
insulating material.
5. The method according to claim 1, wherein the concentration of
the compound to be measured in a liquid phase or a gas phase in
soil is reduced by jetting a liquid or a gas to the soil.
6. The method according to claim 1, wherein the concentration of
the compound to be measured in a liquid or gas phase in soil is
reduced by removal or decomposition of the compound.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of grasping the
distribution state of a compound in soil. More specifically, the
present invention relates to a method of detecting the
high-concentration region direction of a compound in soil using a
frequency-converting element or the like. In this specification,
the term "soil" includes all components composed of a solid, a
liquid and a gas, for forming the earth and groundwater.
[0003] 2. Related Background Art
[0004] There are prior arts such as "Search for chemical substance
source by means of submerged compass system" and "Research on
compass for searching chemical substance source in water imitating
crayfish" (see "Data of the research conference on a chemical
sensor by the Institute of Electrical Engineers" VOL. CHS-03, NO.
56-86; PAGE. 75-80; (20031128-20031129), Hiroshi Sakata, Seigo Ito,
Hiroshi Ishida, Toyosaka Moriizumi, (Tokyo Institute of
Technology), "Convention record of the Institute of Electronics,
Information and Communication Engineers" VOL. 2004, Electronics 2;
PAGE. 151; (20040308), Hiroshi Sakata, Hiroshi Ishida, Toyosaka
Moriizumi, (Tokyo Institute of Technology) (hereinafter, referred
to as "Document 1" and "Document 2", respectively)).
[0005] Hereinafter, a conventional method of detecting the
direction of the position of a pollutant will be described with
reference to Documents 1 and 2.
[0006] Document 1 discloses "A compass for searching an odor source
in water capable of detecting a chemical substance by actively
sucking water around the substance was developed. A slit was
arranged immediately before a sensor electrode arranged at the
inlet of a circular pipe to enable a sucked chemical substance to
be surely captured by the sensor electrode. In addition, it has
been confirmed that the range of directions to be sucked by each
slit can be controlled by changing the number of slits and the
width of each slit. A submerged compass having 4 sensor electrodes
was produced. As a result, observing which sensor responds allows
one to judge whether a substance source is present in the range of
the forward direction .+-.20.degree., or left or right region
except for the range. The compass system was attached to a linear
actuator to perform an experiment for searching a chemical
substance source in still water in a water tank. As a result, the
search was successful at a high probability."
[0007] Document 2 discloses "A crayfish can attract not only an
odor isotropically from its surrounding but also a flow intensively
from one of its right and left sides by using its fan-like
appendages called gnathopods. The present document realized a
function of sucking from only a specific direction, by imitating
the gnathopods of a crayfish to separately use right and left
gnathopod structures. The use of a gnathopod structure makes it
possible to realize a system for searching the presence or absence
of a source by efficiently collecting signals from various places
around the system."
[0008] Document 1 describes a system for detecting a chemical
substance by actively sucking the substance through a slit. When
the system is applied to the search for the direction of a volatile
chlorinated organic compound (VOC) in soil, differences in the rate
of a sucking stream and the rate of a sucking wind occur owing to
differences in granularity and porosity in the soil other than the
slit, to thereby destabilize a concentration signal. In addition,
in such system as described in Document 2, suction causes
turbulence to make a concentration signal more unstable than that
in the present invention. As described above, a suction system
destabilizes a concentration signal and deteriorates a detection
lower limit. Therefore, such system is not suitable for detecting a
VOC at an extremely low concentration and for detecting a direction
of interest. In addition, the system described in Document 2 does
not express a suction function in a condition like soil where the
amount of dirt is larger than that of water because the wing of a
gnathopod structure does not move in such condition, although the
system can express the suction function in water.
[0009] Investigation into the distribution of pollution by a
chlorinated organic compound such as trichloroethylene that
pollutes soil has been conducted by detecting and measuring a
volatile chlorinated organic compound by means of a detecting tube
in a boring hole at a certain interval or in a shallow excavated
hole. However, tracking down a region where a high concentration of
chlorinated organic compound is present is extremely difficult. A
chlorinated organic compound that has polluted soil is dissolved
into groundwater and soil water to diffuse, and is vaporized to
diffuse and move in the soil. The movement causes the compound to
distribute in the soil while forming a certain concentration
gradient in the soil.
[0010] A large number of methods each involving analyzing a gas
sample collected from soil by means of an analyzer such as a gas
chromatograph have been adopted for detecting a chlorinated organic
compound such as trichloroethylene. In addition, Japanese Patent
Application Laid-Open No. 2004-108913 discloses a gas measurement
method including: subjecting a gas to be measured to oxidation and
reduction decomposition in a reaction tube to transform the gas to
be measured into a decomposition product; and detecting the gas by
means of a chemical reaction between the decomposition product and
a quartz resonator electrode material or adsorption property
between them. However, the method is not intended for detecting a
distribution. In addition, Japanese Patent No. 3443632 discloses,
as a technique for direct detection, a method of measuring a
gaseous chlorinated organic compound by means of a quartz resonator
having an electrode to which lipid is applied. However, the method
is intended for detecting the concentration of a gaseous
chlorinated organic compound, and it is not possible to detect the
distribution state of a chlorinated organic compound in soil in
soil water, ground water, or the like.
[0011] Japanese Patent No. 2759683 discloses the constitution of a
quartz resonator for detecting a compound in water by means of a
quartz vibrating element. Here, a material for adsorbing or
absorbing the compound in water is applied to one surface of one
electrode of the quartz resonator, and one surface of the other
electrode of the quartz resonator is coated with an electrically
insulating jacket so that the electrode is out of contact with
water and is in contact with the air.
[0012] The above shape has a large jacket with which the quartz
resonator is coated, and involves the difficulty in grasping a
change in distribution of the concentration of a VOC.
[0013] Japanese Patent No. 3292866 discloses a method of detecting
the flow of a gas or an odor as a gas. The method involves:
arranging a large number of sensors for detecting a gas on a plane
with a spatial spread; and grasping the flow of a gas or odor upon
response by each sensor element. However, if it is assumed that the
method is used for measurement in soil, the sensors must be
installed in a limited well or excavated hole. Therefore, it is
difficult to detect the flow and direction of a gas when it is
difficult to arrange the sensors widely and two-dimensionally or
three-dimensionally.
SUMMARY OF THE INVENTION
[0014] The present invention has been made in order to solve the
above-described problems of the prior art, and an object of the
present invention is to provide a method of detecting the
high-concentration region direction of a compound to be measured in
soil up to an extremely low-concentration region as compared to a
conventional method.
[0015] Another object of the present invention is to provide a
method of detecting a direction of a high-concentration region of a
compound to be measured in soil, including utilizing a difference
in diffusion change of a concentration of the compound to be
measured in soil from a high-concentration region and a
low-concentration region in a recovery phenomenon in which a
concentration of the compound increases again after reducing the
concentration.
[0016] In the present method, it is preferable that the compound to
be measured is a chlorinated organic compound such as
trichloroethylene or tetrachloroethylene.
[0017] In the present method, it is preferable that the detection
is carried out using a frequency-converting element.
[0018] In the present method, it is preferable that the
frequency-converting element includes an electrode having one
surface coated with a material for adsorbing the compound and other
surface coated with an electrically insulating material.
[0019] In the present method, it is preferable that the
concentration of the compound to be measured in a liquid phase or a
gas phase in soil is reduced by jetting a liquid or a gas to the
soil.
[0020] In the present method, it is preferable that the
concentration of the compound to be measured in a liquid or a gas
phase in soil is reduced out by removal or decomposition of the
compound.
[0021] The present invention utilizes, as means for changing the
distribution state of a compound to be measured in a liquid phase
or in a vapor phase in soil, a recovery phenomenon in which the
concentration of a compound to be measured at a point of
measurement increases again after the concentration has been
reduced. The present invention provides a method of detecting the
high-concentration region direction of a compound to be measured in
soil, including utilizing the phenomenon to measure differences in
a compound concentration and various physical properties related
thereto due to a difference in diffusion change from a
high-concentration region and a low-concentration region.
[0022] According to the present invention, there is provided a
method of easily detecting the direction in which a chemical
substance in soil is distributed at a high concentration with high
efficiency and high accuracy in detecting the distribution position
and distribution region of the chemical substance in soil. The
method has effects on not only an azimuth such as east, west, south
or north but also a direction such as a vertical direction or an
oblique direction. Examples of soil include soil present on the
earth and soil present on the ground as a result of excavation, and
the methods has an effect on each such soil.
[0023] Other features and advantages of the present invention will
be apparent from the following description taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic view showing the arrangement structure
of a quartz resonator.
[0025] FIG. 2 is a schematic view showing the constitution of an
apparatus for a soil tank experiment.
[0026] FIG. 3 is a graph showing the measured results of an azimuth
detection experiment (distance: 3 cm).
[0027] FIG. 4 is a graph showing the measured results of an azimuth
detection experiment (distance: 4 cm).
[0028] FIG. 5 is a graph showing the measured results of an azimuth
detection experiment (distance: 5 cm).
[0029] FIG. 6 is a view showing the constitution of a model used in
Examples.
[0030] FIG. 7 is a graph showing the measured results of an azimuth
detection experiment (distance 7 cm).
[0031] FIG. 8 is a schematic view showing an example of a sampling
point of a detection apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] As detection means in the present invention, a
frequency-converting element can be used. But elements other than
the frequency-changing element can be also used, and examples
thereof include conventional detection means such as surface
acoustic wave element type, semiconductor type, optical type,
chromatography type, electrical resistance type, and mass
spectrometry type means.
[0033] Therefore, a substance to be detected by the method of the
present invention is not limited to a substance to be detected by a
frequency-converting element. That is, the substances and the like
to be detected by the method of the present invention can include
chemical substances that can be detected by conventional detection
means and all various physical and electrical properties related to
the chemical substances. That is, the object to be detected include
a hydrogen ion concentration, a temperature, and an electric
conductivity. Not only the case where a hydrogen ion concentration,
a temperature, and an electric conductivity are related to the
chemical substances themselves but also the case where they are
related to the decomposition products, decomposition reaction heat,
and the like of the chemical substances is also included in the
present invention.
[0034] A substance used for coating which an electrode of the
frequency-converting element in the present invention is not
limited as long as it can adsorb or absorb a compound to be
measured.
[0035] In the present invention, a recovery phenomenon in which the
concentration of a compound to be measured in soil at a point of
measurement increases again after the concentration has been
reduced may be induced by any method. The any method includes, as a
removal method, an injection-type removal method involving
injecting water, air or the like having a low concentration of a
compound to be measured, and further a suction-type removal method,
an absorbent-type removal method, an adsorbent-type removal method,
and a substitution-type removal method, and as a decomposition
method, a ultraviolet degradation method, a thermal decomposition
method, a chemical decomposition method, and a biological
decomposition method. The removal method, the decomposition method
or the like may be used in combination. As described above, a
phenomenon is utilized in which, after a low-concentration region
has been formed around a point of measurement, a difference in
concentration between directions is larger than that prior to
removal, decomposition or the like during or after re-diffusion.
Even in the case where detection means other than a
frequency-changing element is used, a method suitable for each
detection means is desirably applied after such phenomenon has been
induced on the basis of the same principle. Examples of such means
include: various sensors each having multiple detection points or
detection surfaces; detection means having multiple diffusion
introduction ports; and detection means with its sampling direction
of a detection direction made variable.
[0036] The ground may be subjected to a treatment such as heating
for the purpose of promoting the recovery phenomenon. Also, the
ground may be perforated with a cave hole or may be provided with a
barrier for preventing mixing for each direction for the purpose of
improving the direction accuracy of the recovery phenomenon.
[0037] The present invention will be described in more detail by
way of the following Examples.
EXAMPLE 1
[0038] A resonance frequency was applied to a quartz resonator
having a resonance frequency of 9 MHz (electrode diameter: 5 mm),
and was measured with a frequency counter. In the quartz resonator,
one surface of one electrode of the quartz resonator was coated
with a vinyl resin for electrical insulation and one surface of the
other electrode of the quartz resonator was coated with polystyrene
to serve as a material for adsorbing trichloroethylene. As shown in
FIG. 1, two quartz resonators each having the coated electrode were
arranged in such a manner that the electrode surfaces coated with
polystyrene would be opposite to each other and the central lines
of the two quartz resonators would deviate from each other by 5 mm.
In FIG. 1, reference numeral 1 denotes a sensor (1); 2, a sensor
(2); 3, a quartz resonator; 4, an adsorbing material; 5, insulating
coating; and 6, a water injection pipe.
[0039] FIG. 2 shows the constitution of an experimental apparatus
in a small soil tank. In FIG. 2, a part where the above two quartz
resonators are combined is represented as a sensing unit. 5 ml of a
700-ppm VOC solution (trichloroethylene) were injected into a small
soil tank (containing 320 g of soil and 60 ml of water), and
trichloroethylene was diffused in the soil. Then, a quartz
resonator part of the sensing unit was inserted into the soil to
perform measurement. In FIG. 2, reference numeral 1 denotes a
sensor (1); 2, a sensor (2); 7, a sensor unit; 8, injected water
for distorting a concentration gradient; 9, an injected VOC
solution; 10, a VOC concentration gradient; and 11, a sensor
position.
[0040] Detection at a distance of each of 3 cm (position A in FIG.
2), 4 cm (position B in FIG. 2), and 5 cm (position C in FIG. 2)
from a pollution source was investigated.
[0041] Data on the resonance frequency of a quartz resonator was
acquired, and then 1 ml of water was injected between the two
quartz resonators to measure the resonance frequency of each of the
two quartz resonators.
[0042] Out of the two quartz resonators, a quartz resonator on the
side of the VOC pollution source was represented as the sensor (1)
and the other quartz resonator was represented as the sensor (2).
FIG. 3 shows the measured results at a distance of 3 cm. FIG. 4
shows the measured results at a distance of 4 cm. FIG. 5 shows the
measured results at a distance of 5 cm.
[0043] In FIG. 3, analysis of the behavior of a change in resonance
frequency of each of the two quartz resonators reveals that the
resonance frequency of the quartz resonator on the side of a higher
concentration returns to the frequency changing state before
injection of water faster than the frequency of the quartz
resonator on the side of a lower concentration. It has been
confirmed that the detection of the difference in behavior between
the two quartz resonators enables the azimuth in which soil is
polluted at a high concentration to be detected. Similar behavior
was observed in each of FIGS. 4 and 5.
[0044] As shown in FIGS. 3, 4 and 5, the method of the present
invention allows the azimuth of a VOC pollution position in soil to
be detected.
[0045] Of course, detection can be performed by subjecting a quartz
resonator to an electrical insulating treatment except for that
disclosed in this example or by changing an interval distance
between quartz resonators.
EXAMPLE 2
[0046] The sensing unit shown in Example 1 was used. Soil (4 kg of
mountain gravel) was fed into a hollow tray. 200 ml of an aqueous
solution of trichloroethylene (700 ppm) as a pollution source were
added. An experiment for detecting a pollution azimuth in a
pollution model produced by adding 600 ml of water (tap water) to
the side opposite to the contamination source was conducted. FIG. 6
shows the constitution of the model used in this example. FIG. 7
shows the measured results at a distance of 7 cm from the pollution
source. A difference in behavior between two quartz resonators was
detected even in the case where the amount of soil was increased to
be about 10 times as large as that in Example 1, the amount of
trichloroethylene was increased to be about 100 times as large as
that in Example 1, and the distance from the pollution source was
extended to 7 cm. This detection showed that the azimuth polluted
at a high concentration in soil was on the side of the sensor (1).
In FIG. 6, reference numeral 7 denotes a sensor unit; 12, a VOC
pollution source; and 13, 4 kg of soil.
EXAMPLE 3
[0047] FIG. 8 shows an example of a sampling equipment for the case
where the concentration is reduced by decomposition. A
trichloroethylene concentration was reduced by ultraviolet
degradation. Turning an ultraviolet lamp off resulted in the
recovery of a trichloroethylene concentration in a pipe partitioned
by a barrier into two chambers. A difference in trichloroethylene
concentration between the two chambers was able to be detected. The
detection showed that the azimuth polluted at a high concentration
in soil was on the side of a diffusion introduction slit (1). In
FIG. 8, reference numeral 14 denotes a detection apparatus: gas
chromatograph (schematic view) (gas suction function included); 15,
the diffusion introduction slit (1) (enlarged view); 16, a
diffusion introduction slit (2) (enlarged view); 17, a pipe for
forming a slit for each direction (enlarged view); 18, a piping
system for introduction to the detection apparatus after separate
sampling from two chambers (schematic view); 19, an ultraviolet
lamp; 20, a barrier; and 21, the ground.
[0048] As described above, according to the present invention,
there is provided a method of detecting a direction of with which
the high-concentration region of a compound to be measured
distributing in soil can be detected.
[0049] Those to be detected by the present invention can include
all chemical substances for each of which detection means is
available and various physical properties related to the chemical
substances.
[0050] This application claims priority from Japanese Patent
Applications No. 2004-315845 filed on Oct. 29, 2004 and No.
2005-212918 filed on Jul. 22, 2005, which are hereby incorporated
by reference herein.
* * * * *